Psychologist W.J. in the year 1890 asserted that the self can be interpreted and theoretically distinguished in two ways of "I" and "me", wherein "I" is reflective of the subject of experience and "me" is reflective of the object of experience. As a result, "me" is the object observed, whereas, "I" is a non-physical entity that does the observing. "I" cannot be directly studied because it is experiential and subjective in essence and often denoted as the "soul", which cannot be observed with the naked eyes or reported by an individual themselves. "I" is beyond the reach of researchers wishing to conduct scientific investigations.
The existence of "I" has been asserted by multiple studies by emphasizing how an individual's sense of existence remains unaltered throughout their lifetime despite the occurrence of major life events such as cognitive and physical decline associated with aging. As a result, "I" is indicative of an unchanging sense of self that is pervasive in essence and persists even after one's attitude, physical outlook, feelings, and behaviors are susceptible to change due to learning, circumstances, and aging. The self experiencing these changes remains constant and, as a result, endures and continues to exist.
"I" has been referred to as the ontological self that can only be directly experienced or described by the person and is immaterial. As a result, it cannot be studied through scientific investigation. On the contrary, "me" has been referred to as the epistemological self that reflects on an individual's self-awareness and consists of self-referential content. It can be described and, in this way, studied through the methodologies used in material science.
Theorists have questioned whether "I" seemingly exists and directs what one experiences or if it is only a passive observer to everything an individual is going through. The dynamic nature of "I" has also been probed along the lines of whether it is subject to change due to the changing circumstances or if it remains unaltered throughout one's lifetime.